IN-CYCLINDER IMAGING APPARATUS AND METHOD

Abstract

An in-cylinder imaging apparatus is provided for an internal combustion engine defining a combustion chamber. The in-cylinder imaging apparatus includes a high-speed imaging device such as a high-speed digital camera. A borescope is provided in communication with the combustion chamber and is operable to communicate images of the combustion chamber to the high-speed imaging device. A high intensity light source, for example, a xenon light source, is operable to substantially illuminate the combustion chamber. The high-speed imaging device and borescope are in axial alignment with respect to each other and are mounted with respect to the internal combustion engine. A method of imaging the combustion chamber of the internal combustion engine during engine operation employing the disclosed in-cylinder imaging apparatus is also provided.

Full Text

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IN-CYLINDER IMAGING APPARATUS AND METHOD
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of United States Provisional Patent
Application No. 60/864,016, filed November 2, 2006, and which is hereby incorporated
by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to an apparatus and method for imaging a
combustion chamber of an internal combustion engine during engine operation.
BACKGROUND OF THE INVENTION
[0003] Engineers typically rely on combustion analysis when developing combustion
chambers to increase the operating efficiency and performance of an internal combustion
engine. Typically engineers have limited information about the combustion occurring
within the combustion chamber of an operating or firing engine. This information may
include items such as in-cylinder pressure indexed to engine rotation, thermal mapping,
etc. However, because of the harsh environment (high pressure, high temperature, etc.)
present within the combustion chamber while the engine is operating, it is difficult to
obtain a visual image of the combustion process occurring within the combustion
chamber.
SUMMARY OF THE INVENTION '
[0004] An in-cylinder imaging apparatus is provided for an internal combustion
engine defining a combustion chamber. The in-cylinder imaging apparatus includes a
high-speed imaging device, such as a high-speed digital camera. A borescope is provided
in communication with the combustion chamber and is operable to communicate images
of the combustion chamber to the high-speed imaging device. A high intensity light
source, such as a xenon light source, is operable to substantially illuminate the

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combustion chamber. The high-speed imaging device and borescope are mounted with
respect to the internal combustion engine.
[0005] In a preferred embodiment, the high-speed imaging device is generally axially
aligned with the borescope. Additionally, the high-speed imaging device is preferably
mounted with respect to the internal combustion engine with a bracket having natural
frequency modes greater than the inducing function of the internal combustion engine. A
window formed, for example, from quartz may be disposed between the borescope and
the combustion chamber to protect the borescope from the high pressures and
temperatures present within the combustion chamber during operation of the internal
combustion engine.
[0006] A prism formed, for example, from sapphire, may be disposed between the
high intensity light source and the combustion chamber. The prism is preferably operable
to disperse light from the high intensity light source into the combustion chamber. A
fiber optic bundle may be provided to communicate light from the high intensity light
source to the prism.
[0007] A method of imaging a combustion chamber of an internal combustion engine
during engine operation is also provided. The method includes the steps of: A) mounting
a borescope with respect to the internal combustion engine and in optical communication
with the combustion chamber; B) mounting a high-speed imaging device with respect to
the internal combustion engine and generally in axial alignment with the borescope such
that the borescope is operable to communicate images from within the combustion
chamber to the high-speed imaging device; C) illuminating the combustion chamber with
light from a high intensity light source; and D) capturing the images of the combustion
chamber with the high-speed imaging device while the internal combustion engine is
operating.
[0008] The method may further include cooling the borescope with chilled and/or
compressed gas. The step of illuminating the combustion chamber may include
employing a dispersion prism to disperse the light into the combustion chamber.
Furthermore, the step of mounting the high-speed imaging device with respect to the
internal combustion engine may include the steps of: A) affixing a bracket to the internal

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combustion engine; B) machining the bracket to accept the high-speed imaging device
while affixed to the internal combustion engine to ensure alignment between the high-
speed imaging device and the borescope; and C) mounting the high-speed imaging device
to the bracket. Additionally, the step of mounting the high-speed imaging device with
respect to the internal combustion engine may further include the step of D) tuning the
bracket such that the natural frequency modes of the bracket are greater than the inducing
function of the internal combustion engine.
[0009] The above features and advantages and other features and advantages of the
present invention are readily apparent from the following detailed description of the best
modes for carrying out the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 is a cross sectional view of a portion of an internal combustion
engine having an in-cyUnder imaging apparatus mounted thereto;
[0011] Figure 2 is a cross sectional view illustrating aspects of a borescope of the in-
cylinder imaging apparatus; and
[0012] Figure 3 is a magnified cross sectional view illustrating aspects of a high
intensity light source of the in-cylinder imaging apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] Referring to the drawings wherein like reference numbers correspond to like
or similar components throughout the several figures, there is shown in Figure 1 a cross
sectional view of a portion of an internal combustion engine 10. The internal combustion
engine 10 has an in-cylinder imaging apparatus 12 mounted thereto. The internal
combustion engine 10 includes a cylinder head 14 and a cam cover 16. The cylinder
head 14 partially defines a combustion chamber 18 where a fuel is combusted with air
during operation of the internal combustion engine 10. The cylinder head 14 is
preferably formed from cast metal including, but not limited to,, aluminum, iron, steel,
magnesium, etc. The cylinder head 14 has a deck portion 20 configured to mate to a

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cylinder block, not shown, of the internal combustion engine 10. Additionally, the
cylinder head 14 includes a spring deck portion 22 operable to provide a mounting
surface for components of a valvetrain, not shown. The deck portion 20 and spring deck
portion 22 cooperate to define a cooling jacket 24 through which coolant flows to effect
cooling of the cylinder head 14. The spring deck portion 22 is subject to lubrication oil
splashed from the valvetrain during operation of the internal combustion engine 10. The
cam cover 16 sealingly engages the cylinder head 14 to retain the lubrication oil within
the internal combustion engine 10.
[0014] The in-cylinder imaging apparatus 12 includes a high-speed imaging device
26, borescope 28, and high intensity light source 30. The high-speed imaging device 26
is, for example, a digital camera with the capability of capturing images at a rate of, for
example, up to 160,000 frames per second, in one embodiment, however other camera
speeds may be used. The high-speed imaging device 26 is axially aligned with the
borescope 28. The borescope 28 is in communication with the combustion chamber 18
and is operable to optically communicate images from within the combustion chamber 18
to the high-speed imaging device 26.
[0015] The high-speed imaging device 26 is mounted to the internal combustion
engine 10 by a bracket 32. The bracket 32 also maintains the axial alignment between
the high-speed imaging device 26 and the borescope 28. The bracket 32 is removably
mounted to the cylinder head 14 by fasteners 34. The bracket 32 is formed, for example,
from metal, such as thick gauge steel, having sufficient structural rigidity to effectively
hold the high-speed imaging device 26 in relation to the borescope 28, to effect rigid
motion between the internal combustion engine 10, borescope 28 and high-speed imaging
device 26. In some embodiments, the bracket 32 is analyzed and tuned to ensure that the
natural frequency modes of the bracket 32 are substantially above any modes of
excitation or inducing function, such as the firing order of the internal combustion engine
10, to avoid resonances that may damage components within the borescope 28 and/or
high-speed imaging device 26. An "inducing function" is an excitation pattern or input
relationship which produces a vibration mode, such as the pattern or sequence of firing an
engine. The bracket 32 is machined to accept the high-speed imaging device 26 when

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mounted on the internal combustion engine 10 in order to provide precise axial alignment
with the borescope 28. A source of pressurized and chilled gas 36, such as air, is
provided as a means to cool the borescope 28.
[0016] The high intensity light source 30 is operable to, for example, provide white
light to the combustion chamber 18 to enhance the images provided by the borescope 28
to the high-speed imaging device 26. The high intensity light source 30 is preferably a
xenon light source; however, those skilled in the art of optics and lighting will recognize
other sources of high intensity light may be used while remaining within the scope of that
which is claimed. Light from the high intensity light source 30 is communicated via a
fiber optic bundle 38 to a dispersion prism 40. The dispersion prism 40 is operable to
disperse the light from the high intensity light source 30 into the combustion chamber 18.
The dispersion prism 40 of this embodiment is formed from a crystalline material,
including, but not limited to, sapphire.
[0017] Referring now to Figure 2, there is shown a cross sectional view illustrating
components of the in-cylinder imaging apparatus 12. A generally tubular sleeve 42
extends through a bore 44, defined by the spring deck portion 22 of the cylinder head 14,
and at least partially through a bore 46, defined by the deck portion 20 of the cylinder
head 14. The bores 44 and 46 are formed by machining the cylinder head 14. The sleeve
42 may be fixed in relation to the cylinder head 14 through an interference fit or by an
adhesive sealant, such as epoxy. The sleeve 42 is formed from a material having similar
thermal expansion characteristics as the cylinder head 14 such that as the temperature of
the cylinder head 14 increases, the sleeve 42 will remain fixed with respect to the
cylinder head 14. The sleeve 42 is operable to seal the coolant jacket 24 from the
combustion chamber 18, borescope 28, and spring deck portion 22. Additionally, the
sleeve 42 is operable to prevent the lubricating oil from entering the cooling jacket 24
from the spring deck portion 22 or contacting the borescope 28.
[0018] An outer sleeve 48 extends through the cam cover 16, shown in Figure 1, and
coaxially engages the sleeve 42. An o-ring seal 50 is disposed about the outer periphery
of the sleeve 42 and is operable to sealingly engage the outer sleeve 48. A window 52 is
provided between the borescope 28 and the combustion chamber 18 and operates to

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protect the borescope 28 from the heat and pressure formed within the combustion
chamber 18 during operation of the internal combustion engine 10. The window 52 is
formed from a crystalline material such as quartz; however, those skilled in the art will
recognize other materials that may be used including, but not limited to, sapphire and
spinel, while remaining within the scope of that which is claimed.
[0019] Referring now to Figure 3 there is shown a cross sectional view further
illustrating components of the in-cylinder imaging apparatus 12. A generally tubular
sleeve 54 extends through a bore 56, defined by the spring deck portion 22 of the cylinder
head 14, and at least partially through a bore 58, defined by the deck portion 20 of the
cylinder head 14. The bores 56 and 58 are formed by machining the cylinder head 14.
The sleeve 54 may be fixed in relation to the cylinder head 14 through an interference fit
or by an adhesive sealant, such as epoxy. The sleeve 54 is formed, for example, from a
material having similar thermal expansion characteristics as the cylinder head 14 such
that as the temperature of the cylinder head 14 increases, the sleeve 54 will remain fixed
with respect to the cylinder hea.d 14. The sleeve 54 is operable to seal the coolant jacket
24 from the combustion chamber 18, fiber optic bundle 38, dispersion prism 40, and
spring deck portion 22. Additionally, the sleeve 54 is operable to restrict the movement
of lubricating oil from entering the cooling jacket 24 from the spring deck portion or
contacting the fiber optic bundle 38 and dispersion prism 40. An outer sleeve 60 extends
through the cam cover 16 and coaxially engages the sleeve 54. An o-ring seal 62 is
disposed about the outer periphery of the sleeve 54 and is operable to sealingly engage
the outer sleeve 60.
[0020] A method of imaging the combustion chamber 18 of the internal combustion
engine 10 during engine operation is also provided. The method includes the steps of:
A) mounting the borescope 28 with respect to the internal combustion engine 10 and in
communication with the combustion chamber 18; B) mounting the high-speed imaging
device 26 with respect to the internal combustion engine 10 and generally in axial
alignment with the borescope 28 such that the borescope 28 is operable to communicate
images from within the combustion chamber 18 to the high-speed imaging device 26; C)
illuminating the combustion chamber 18 with light from the high intensity light source

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30; and D) capturing the images of the combustion chamber 18 with the high-speed
imaging device 26 while the internal combustion engine 10 is operating.
[0021] The method further includes cooling the borescope 28 with chilled and
compressed gas from the chilled and compressed gas source 36. The step of illuminating
the combustion chamber 18 includes employing a dispersion prism 40 to disperse the
light into the combustion chamber 18. Furthermore, the step of mounting the high-speed
imaging device 26 with respect to the internal combustion engine 10 preferably include
the steps of: A) affixing the bracket 32 to the internal combustion engine 10; B)
machining the bracket 32 to accept the high-speed imaging device 26 while affixed to the
internal combustion engine 10 to ensure alignment between the high-speed imaging
device 26 and the borescope 28; and C) mounting the high-speed imaging device 26 to
the bracket 32. Additionally, the step of mounting the high-speed imaging device 26 with
respect to the internal combustion engine 10 further includes the step of D) tuning the
bracket 32 such that the natural frequency modes of the bracket 32 are greater than the
inducing function of the internal combustion engine 10.
[0022] By incorporating the high-speed imaging device 26 within the in-cylinder
imaging apparatus 12, the ability to obtain contiguous high-speed images of the
combustion chamber 18 during engine operation will provide engine designers with
additional information necessary to investigate combustion characteristics of the internal
combustion engine 10. These combustion characteristics may include information such
as, cylinder wall wetting by fuel, fuel spray characteristics, soot generation within the
combustion chamber 18, flash boiling, etc. The in-cylinder imaging apparatus 12 may be
used with both spark ignited and compression ignited internal combustion engines and
may be a particularly useful tool in designing spark ignited direct injection and
compression ignited engines, which require careful attention to be paid in the design of
the combustion chamber, piston dome, and fuel spray characteristics and timing.
[0023] While the best modes for carrying out the invention have been described in
detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.

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CLAIMS
1. An in-cylinder imaging apparatus for an internal combustion
engine defining a combustion chamber, said in-cylinder imaging apparatus comprising:
a high-speed imaging device;
a borescope in optical communication with the combustion
chamber and operable to communicate images of the combustion chamber to said high-
speed imaging device;
a high intensity light source operable to substantially illuminate the
combustion chamber; and
wherein said high-speed imaging device and said borescope are
mounted with respect to the internal combustion engine.
2. The in-cylinder imaging apparatus of claim 1, wherein said high-
speed imaging device and said borescope are axially aligned.
3. The in-cylinder imaging apparatus of claim 1, further comprising a
protective window disposed between said borescope and the combustion chamber.
4. The in-cylinder imaging apparatus of claim 3, wherein said
protective window is formed from at least one of quartz, spinel, and sapphire.
5. The in-cylinder imaging apparatus of claim 1, wherein said high-
speed imaging device is a high-speed digital camera.
6. The in-cylinder imaging apparatus of claim 1, wherein said
borescope is cooled with chilled and compressed gas.
7. The in-cylinder imaging apparatus of claim 1, further comprising a
bracket operable to mount said high-speed imaging device to said engine.

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8. The in-cylinder imaging apparatus of claim 7, wherein said bracket
has natural frequency modes greater than an inducing function of the internal combustion
engine.
9. The in-cylinder imaging apparatus of claim 1, wherein said high
intensity light source is a xenon light source.
10. The in-cylinder imaging apparatus of claim 1, further comprising a
prism disposed between said high intensity light source and the combustion chamber,
wherein said prism is operable to disperse light from said high intensity light source into
the combustion chamber.
11. The in-cylinder imaging apparatus of claim 10, wherein said prism
is formed from sapphire.
12. The in-cylinder imaging apparatus of claim 10, further comprising
a fiber optic bundle disposed between said high intensity light source and said prism, said
fiber optic bundle being operable to communicate said light from said high intensity light
source to said prism.
13. A method of imaging a combustion chamber of an internal
combustion engine during engine operation, the method comprising:
mounting a borescope with respect to the internal combustion
engine and in optical communication with the combustion chamber;
mounting a high-speed imaging device with respect to the internal
combustion engine and in generally axial alignment with said borescope; such that said
borescope is operable to communicate images from within the combustion chamber to
said high-speed imaging device;
illuminating the combustion chamber with light from a high
intensity light source; and

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capturing said images of the combustion chamber with said high-
speed imaging device while the internal combustion engine is operating.
14. The method of claim 13, further comprising cooling the borescope
with chilled and compressed gas.
15. The method of claim 13, wherein illuminating the combustion
chamber includes employing a dispersion prism to disperse said light into the combustion
chamber.
16. The method of claim 13, further comprising protecting said
borescope by placing a window between said borescope and the combustion chamber.
17. The method of claim 16, wherein said window is selected from the
group consisting of quartz, sapphire and spinel.
18. The method of claim 13, wherein mounting said high-speed
imaging device with respect to the internal combustion engine includes:
affixing a bracket to the internal combustion engine;-
machining said bracket to accept said high-speed imaging device
while affixed to the internal combustion engine to ensure alignment between said high-
speed imaging device and said borescope; and
mounting said high-speed imaging device to said bracket.
19. The method of claim 13, wherein mounting said high-speed
imaging device with respect to the internal combustion engine includes:
affixing a bracket to the internal combustion engine;
mounting said high-speed imaging device to said bracket; and
tuning said bracket such that the natural frequency modes of said
bracket are greater than an inducing function of the internal combustion engine.

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20. The method of claim 15, further comprising communicating said
light from said high intensity light source to said prism through a fiber optic bundle.
Dated this 16th day of OCTOBER 2007

An in-cylinder imaging apparatus is provided for an internal combustion
engine defining a combustion chamber. The in-cylinder imaging apparatus includes a
high-speed imaging device such as a high-speed digital camera. A borescope is provided
in communication with the combustion chamber and is operable to communicate images
of the combustion chamber to the high-speed imaging device. A high intensity light
source, for example, a xenon light source, is operable to substantially illuminate the
combustion chamber. The high-speed imaging device and borescope are in axial
alignment with respect to each other and are mounted with respect to the internal
combustion engine. A method of imaging the combustion chamber of the internal
combustion engine during engine operation employing the disclosed in-cylinder imaging
apparatus is also provided.